Hydrated metal(II) complexes of N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl) derivatives of glycine, glycylglycine, threonine, serine, valine and methionine: a monomeric complex and coordination polymers in one, two and three dimensions linked by hydrogen bonding

Abstract

Nine hydrated complexes of Group 2 (alkaline earth) cations with organic ligands which are N-substituted amino acids containing the 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidin-2-yl group have been structurally characterized. The octahydrated calcium glycinate complex, where the six-coordinate Ca cation lies on an inversion centre in the space group P\bar 1, forms a finite (zero-dimensional) complex. The hexahydrated barium glycinate complex contains eight-coordinate Ba and it is isostructural with the known Sr analogue, and its one-dimensional coordination polymer takes the form of a simple chain. The octahydrated calcium and strontium threonine complexes are isostructural, with eight-coordinate cations lying on twofold rotation axes in the space group C2: the one-dimensional coordination polymers take the form of a chain of spiro-fused rings and a similar chain of spiro-fused rings is found in the heptahydrated barium serine complex, although here the ten-coordinate cation lies in a general position. In the tetrahydrated strontium and barium glycylglycinate complexes, the eight-coordinate cations lie on twofold rotation axes in the space group C2/c, but in the Sr complex the coordination polymer is a chain of spiro-fused rings, while in the Ba complex the coordination polymer forms deeply puckered sheets. There are two types of Ca site in the hexahydrated calcium valine complex: one is eight coordinate and gives rise to a two-dimensional coordination polymer, while the other is seven coordinate forming a finite, zero-dimensional coordination complex. In the heptahydrated barium methionine complex, the coordination polymer is three dimensional. In all of the complexes, the coordination aggregates are further linked by an extensive series of hydrogen bonds.

Adsorption of Metal Ions on an Activated Carbon/L‐Lysine Derivative Hybrid Compound

“…However, the N-amino acid side-chain deviates from this plane. The bond lengths in the pyrimidine group are similar to those of analogous derivatives, [12][13][14] which points to an extensive electronic delocalisation in this moiety. This results in a bipolar character for the pyrimidine with a positive charge located on the NHC(2)N(3)C(4)NH 2 group and a negative one on C(5) NO (Scheme 2).…”

“…The pyrimidine moiety shows similar structural and electronic features to analogous compounds mentioned above. [12][13][14] The C(5)NO group is oriented trans to C(6) in such a way that its oxygen atom O(5) is able to form an intramolecular N-H···O hydrogen bond in an S(6) motif, which is coplanar with the pyrimidine ring. However, the N-amino acid side-chain deviates from this plane.…”

“…Scheme 1. Structural studies on these type of derivatives have shown the existence of a strong dipole at the aromatic moieties due to the electron-withdrawing character of their C(5) NO and C(6)O substituents. [12][13][14] The existence of such a dipole is common to all compounds of this class as the polymethylene separators (S) are not conjugated with the pyrimidine residues. This bipolar character means that the energy differences between their HOMO and LUMOs are small and that the energy of these orbitals is close to the energy values calculated for the frontier orbitals of modelled arene active sites present on the surface of an activated carbon (AC).…”

Non-covalent Functionalization of Graphene to Tune Its Band Gap and Stabilize Metal Nanoparticles on Its Surface

“… 13 − 18 This interaction is driven not only by van der Waals forces but also by a strong polar interaction, 19 arising from the electron-withdrawing π cloud by the exocyclic C(5)-NO group. 20 − 22 Thus, it is expected that this mechanism is preserved when compounds similar to those of Scheme 1 a but with different substituent R are attached to graphene. This will result in graphene–pyrimidine derivative hybrids having on their surface the R function of the pyrimidine derivative.…”

“…We have previously reported that the attachment of C(5)­nitroso-pyrimidine derivatives (Scheme a) onto the surface of some carbon materials takes place by π stacking between the planar pyrimidine-conjugate residue and the arene centers, Cπ, of the graphene surface. − This interaction is driven not only by van der Waals forces but also by a strong polar interaction, arising from the electron-withdrawing π cloud by the exocyclic C(5)-NO group. − Thus, it is expected that this mechanism is preserved when compounds similar to those of Scheme a but with different substituent R are attached to graphene. This will result in graphene–pyrimidine derivative hybrids having on their surface the R function of the pyrimidine derivative.…”